ALCOHOL SOLUBLE PROTEIN. 



57 



temperature as possible. This casein may, if a verj- pure product 

 is required, be redissolved, reprecipitated, and the treatment 

 with alcohol and ether repeated ; the casein is finally dried at 

 100 to 105 C., and is then a white amorphous powder ; if casein 

 containing water is dried it forms horny masses. 



Van Slyke and Baker have quite recently described a method 

 for preparing pure casein from undiluted milk by treatment 

 with normal acid, preferably lactic, or a mixture of 1 part hydro- 

 chloric and 2 parts acetic acid. The acid is introduced below 

 the surface of the milk, near the bottom, and very close to a 

 mechanical stirrer revolving at high speed. Coagulation occurs 

 throughout the milk, the preparation only takes 10 hours, and 

 after removal of the fat a fine white powder containing only 

 0-1 per cent, ash and 0-80 per cent, phosphorus is obtained. It 

 is free from phosphates, calcium, and products of hydrolysis. 



Alcohol Soluble Protein. Osborne and Wakeman find that 

 a portion of the casein precipitated by acids is soluble in alcohol, 

 and is separated by pouring the alcoholic solution into water ; 

 the composition is C 54-91, H 7-17, N 15-71, S 0-95, P 0-08 ; 

 the proportions of nitrogen by Hausmann's method are the same 

 as casein, and it has distinct acid properties ; it is almost in- 

 soluble iii water, and is precipitated by acids, but is soluble 

 in dilute alkalies and in very dilute acetic acid, and is soluble 

 in 70 per cent, alcohol, though insoluble in absolute alcohol. 



It gives strong tryptophane, Millon's and biuret reactions, and 

 yields a voluminous precipitate with potassium ferrocyanide ; 

 it may be identical with the ^-casein of Lindet, which had an 

 []i> of 30 (the a-casein having [a] D of 116). 



Products of Hydrolysis of Casein. The following composition 

 is given by Chittenden and Painter to the products of hydrolysis 

 of casein (Table X.) : 



TABLE X. 

 CASEOSES PRODUCED BY THE ACTION OF PEPSIN. 



